Ideal protein concept:Balance is essential

In growing animals, the ideal protein is a concept where the amino acids pattern (defined as a percentage of lysine) maximizes growth, nitrogen retention or another response criterion. In this profile, all indispensable amino acids are equally limiting for performance, just covering the requirements for all physiological functions. Lysine has traditionally been used as a reference because it is the first limiting amino acid for growth in pigs. Although the concept of ideal protein was developed in the late 1950s and early 1960s, one of the first reference studies in pigs was published only in 1989. It is frequently assumed that the ideal protein profile does not change for a given growing stage. In practical nutrition, this offers the advantage that the lysine requirement will vary (per kg of feed or per MJ of energy), but not the ideal amino acids profile expressed relative to lysine. Each of these ratios can thus be directly introduced as a constraint in feed formulation.

Existing studies and the already published ideal protein profiles now enable this concept to be applied for each species. Moreover, increased knowledge about the use of amino acids and their factors of variation make it possible, when useful, to break down the concept for each physiological stage within a species.

Using literature reviews and experimental collaborations, Ajinomoto Animal Nutrition Europe proposes ideal protein profiles. These profiles have been published in Ajinomoto Animal Nutrition Europe's technical bulletins (Tables 3, 4 and 5). The ratios for each amino acid are expressed relative to lysine on the digestible basis (SID for swine and true digestibility (TD) for poultry.

Practical interest of the ideal protein

The application of the concept of the ideal protein in feed formulation makes it possible to adjust the supply of the indispensable amino acids to the requirements of animals in order to avoid deficiencies and limit excesses. These excesses, which are mainly caused by protein-rich raw materials, such as soybean meal, provide some amino acids which go beyond the animal's requirements; they have therefore to be catabolised by animals and they are at the origin of the excretion of nitrogen compounds which are transformed into nitrates in the environment. In the implementation of the concept of the ideal protein, feed-use amino acids are indispensable ingredients to optimize the balance of amino acids in feed formulas – meeting objectives of performance, profitability and respect for the environment.